298 PRINCIPLES OF RURAL ECONOMICS 



change in the land, but through his sheer inability to handle 

 it efficiently. When he has already such a quantity under his 

 management that to undertake the management of a few more 

 acres would divide his attention and cause a slightly less effi- 

 cient management of the whole, the question for the farmer is, 

 Will the additional acres add as much to the total product of 

 his whole business as they will cost ? This is different from 

 the question, Will these acres themselves produce as much as it 

 will cost to cultivate them ? The former question alone relates 

 to the marginal productivity of his land. 



The case is even clearer when we assume that the farmer has 

 a fixed quantity of labor and capital at his disposal and is debat- 

 ing the question whether to rent (or buy) a few more or a few 

 less acres. If he uses more land he will spread his labor and 

 capital a little more thinly, that is, he will cultivate his land a 

 little less intensively, which will ordinarily result in a slightly 

 smaller product per acre. This may be more than counterbal- 

 anced by the larger number of acres, but the addition made by 

 the few additional acres will not be their total product. It will 

 be the product of the whole farm when these acres are added, 

 minus the product of the whole farm when these acres are not 

 included. For example, if the farmer with labor and capital at 

 his disposal can grow 50 bushels of corn per acre when he 

 cultivates 40 acres, and only 42 bushels per acre when he culti- 

 vates 50 acres, with the same labor and capital, the additional 

 i o acres are worth at the outside only I oo bushels a year to him, 

 that being the amount added to his total crop by the additional 

 i o acres. If by spreading his labor and capital over 60 acres he 

 gets only 36 bushels per acre, the last 10 acres are worth, at the 

 outside, only 60 bushels, that being the amount by which his 

 total crop is increased by the addition of those acres. Again, 

 if by spreading his capital and labor over 70 acres he succeeds, 

 on the average and in the long run, in getting a crop of only 



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